I have found the following prior art to be relevant:
(1) DE-OS-2641469 PA1 (2) DE-OS-2601506 PA1 (3) DE-PS 213041
The procedure and device according to DE-OS-2641469 may help to economize on water and energy. They cause, however, a pollution of the working fluid, a risk of infection in spite of cleaning after each application, indefinite strain energy due to varying directions of the jet on the impacted areas, and a nuisance from splashing water to the patient and physiotherapist.
The jet massaging device according to DE-OS-2601506 economizes on water and energy; moreover the risk of infection is generally smaller because the impact area is a partition.
However, the device has the disadvantage that, because of the rather small distance between the nozzle and the impact area and the decelerating effect of the stored water that must be passed by jet, lower pressures are available at the impact area for a given pump power.
Especially disadvantageous is, however, the fact that relative movements between the elastic membrane of the device and the connective tissue are necessary during the treatment which may cause disadvantageous tangential strain upon the tissue and even the formation of lesions. Finally a precise guide of the pistol-grip handle requires extraordinary ability of the physiotherapist.
The arrangement of the nozzle according to DE-PS 213041 allows considerable energy and water economies without incurring mechanical or infectious risks for the patient. Here, however, the following disadvantages are found:
1. The bag making up the spray enclosure does not allow sufficient straight movement of the nozzle. Access to the interior for service is difficult.
2. The inclination of the impact vectors changes from one point to the next.
3. From a practical point of view, it appears to be impossible to achieve specified directions of the jet as accurately as required for steady massaging without making use of sophisticated three-dimensional control devices, the more so as an optical control by means of the patient's body is ruled out be deflection of light by spray water drops, even if the bag is assumed to be transparent.
4. Variable aberrations in inclination of the nozzle's axis initiate different consequences as distances between the nozzle and the area impacted change.
5. The total weight of the membrane forming the impact area counteracts the transmitting jet; consequently, relatively small THIN impact areas are demanded. On the other hand, the limitation of the maximal strain which is permissible requires relatively THICK membranes during operation.